COST OF REPRODUCTION AND COST OF PARASITISM IN THE COMMON LIZARD, LACERTA-VIVIPARA

Parasites may play a complex role in shaping patterns of host reproduc tive effort and therefore in determining costs of reproduction in thei r hosts. Parasites may cause a more or less large reduction in the amo unt of energy an individual host may use for reproduction and maintena nce. Irrespective of the parasite-induced reduction in energy intake, infected hosts may either show the same allocation pattern than uninfe cted hosts, or respond to parasitism by changing the proportion of ene rgy allocated to each trait (e.g. increased investment in current repr oduction at the expense of survival). Moreover, hosts may differ in th eir susceptibility to parasites (e.g. hosts with high reproductive eff ort mag show higher vulnerability to parasite infection). Each of thes e hypotheses leads to a pattern of correlation between parasite load, host survival and reproduction. In this paper we compared the predicte d patterns of correlation between parasite load, host survival and rep roduction with those observed for the Lacerta vivipara - haematozoa as sociation. We found that: (1) haematozoa load was positively correlate d with lizard reproductive effort; (2) haematozoa load was not correla ted with host survival; (3) lizards with high reproductive investment suffered higher mortality rare than lizards with low reproductive inve stment. These findings suggest that parasites do not significantly red uce host energy intake, and are in agreement with a shift of the alloc ation rule of parasitized hosts toward reproduction. However, our corr elative study does not allow us to attribute this shift to an adaptive host response to parasites rather than a by-product of a differential susceptibility to parasite infections.